3Fluid printing cylinder

Abstract

Fluid pressure cylinder with: a cylinder base body (12) having a pair of ports (24, 26) for supplying and discharging a pressure fluid and a cylinder chamber (28) into which the pressure fluid is introduced from the ports (24, 26), a piston (18) to which a piston seal (44) is mounted in an installation groove (42) formed on an outer peripheral surface of the piston (18), wherein the piston (18) is displaceable in the axial direction inside the cylinder chamber (28), and a cover member (22) attached to one end side of the piston (18) and having a damping portion (50) that absorbs shocks caused when the piston (18) strikes the cylinder base body (12) at a displacement end position at which the piston (18) is displaced to one end of the cylinder base body (12), wherein a groove portion (46) to which the cover member (22) is attached is formed on the outer peripheral surface of the piston (18) and arranged adjacent to the installation groove (42), wherein an outer diameter of the groove portion (46) is smaller than an outer diameter of the piston (18), characterized in that the cover element (22) further comprises a hook portion (54) projecting toward an inner peripheral side of the piston (18), and that another groove portion (48) which is recessed radially inward relative to the groove portion (46) and to which the hook portion (54) is attached is provided on the outer peripheral surface of the piston (18) between the groove portion (46) and the installation groove (42).

Description

Background of the invention

[0001] The present invention relates to a fluid pressure cylinder for displacing a piston in the axial direction by supplying a pressurized fluid.

[0002] Until now, a fluid pressure cylinder, for example, has been used as a means for transporting workpieces or the like. This cylinder has a piston that is displaced by the supply of a pressurized fluid. In such a fluid pressure cylinder, as described, for example, in German utility model DE 20 2005 013 185 U1, a piston is displaceably arranged inside a tubular cylinder tube, with a piston rod connected to the piston. The piston is displaced by the supply of a pressurized fluid. A damper made of an elastic material is attached to one end surface of the piston to dampen shocks when the piston strikes a wall surface at its displacement end. In addition, a piston seal, which is provided on the outer peripheral surface of the piston, is formed integrally with the damper.

[0003] In a fluid pressure cylinder described in Japanese Patent Laid-Open No. 10-238512, a buffer body retaining groove is machined into one end surface of the piston by cutting or the like. A rubber cushion serving as a damper is mounted in the buffer body retaining groove, which is annular in shape. Furthermore, a piston seal and a wear ring are mounted in annular grooves formed on the outer peripheral surface of the piston. Summary of the invention

[0004] In the fluid pressure cylinder according to DE 20 2005 013 185 U1, the installation groove for attaching the damper is formed on the end surface of the piston. Another installation groove for attaching the guide element is formed separately on the outer peripheral surface of the piston. This makes it necessary to increase the length of the piston to accommodate the formation of the two different installation grooves. This poses the problem of increasing the length of the fluid pressure cylinder. Furthermore, since the damper and the piston seal are integrally formed, even if the required properties, such as material and hardness, of the damper and the piston seal differ, the damper and the piston seal must be made of the same material. This raises concerns that the required properties cannot be achieved.

[0005] In the fluid pressure cylinder according to JP 10-238512 A, it is also necessary to create the buffer body retaining groove by cutting into the end face of the piston, which increases manufacturing costs. Furthermore, when attaching the piston seal and wear ring to the piston, the assembly process is difficult because the outer diameters of the ring grooves for their installation are essentially the same as the outer diameter of the piston. This also increases manufacturing costs.

[0006] In addition, there is a growing need recently to reduce the number of parts in fluid pressure cylinders and to improve manufacturability by improving assembly and work efficiency in assembling the fluid pressure cylinders.

[0007] From US 34 65 650 A, a shock absorber for a piston-cylinder assembly according to the preamble of claim 1 is known. A shock absorbing element made of elastic material is attached to an end portion of the piston and is held on a groove portion of the piston.

[0008] Further end-position damped pressure cylinders are known from DE 101 58 123 B4 and US 3 136 228A.

[0009] It is an object of the present invention to propose a fluid pressure cylinder with which the manufacturing costs can be reduced and the assembly can be simplified.

[0010] This object is essentially achieved by the invention by the features of claim 1.

[0011] Advantageous embodiments of the invention are the subject of the subclaims.

[0012] According to the present invention, in the fluid pressure cylinder, the cover member is attached to one end side of the piston arranged in the cylinder chamber of the cylinder main body, and the damper portion is provided on the cover member to absorb shocks caused when the piston abuts the cylinder main body at a displacement end position at which the piston is displaced to the end of the cylinder main body.

[0013] By attaching the cover member to one end of the piston, shocks generated at the displacement end position are absorbed by the damping portion. Since the outer diameter of the groove portion where the cover member is attached is small relative to the installation groove formed on the outer periphery of the piston and in which the piston seal is installed, the piston seal can be easily installed in the installation groove adjacent to the groove portion.

[0014] Since the grooved portion is formed on the outer peripheral surface of the piston to facilitate the installation of the cover member with the damping portion, it is therefore not necessary to form the grooved portion on an end surface of the piston by a cutting process (e.g., face milling). This can reduce manufacturing costs and improve processability, along with simplifying the assembly of the piston seal.

[0015] Further features, objects, and advantages of the present invention will become apparent from the following description of an exemplary embodiment and the drawings. All described and / or illustrated features, individually or in combination, constitute the subject matter of the invention, regardless of their summary in the claims or their interrelationship. Short description of the drawings Fig. 1 is a sectional view of a fluid pressure cylinder according to an embodiment of the present invention; Fig. Fig. 2 is an exploded section showing a state in which a piston cover is removed from a piston of the fluid pressure cylinder according to Fig. 1 is removed; and Fig. 3 is an enlarged section showing the area around the piston and piston cover in Fig. 1 shows. Description of the preferred embodiments

[0016] As in Fig. 1, a fluid pressure cylinder 10 includes a cylinder tube (cylinder body) 12 formed in a cylindrical or tubular shape, a head cover 14 attached to one end of the cylinder tube 12, a rod cover 16 attached to another end of the cylinder tube 12, a piston 18 slidably disposed inside the cylinder tube 12, a piston rod 20 connected to the center of the piston 18, and a piston cover (cover member) 22 attached to one end side (in the direction of arrow A) of the piston 18.

[0017] A first port 24 and a second port 26 open at positions near one and the other ends of the outer peripheral side of the cylinder tube 12, respectively. A switching device for switching the supply of a pressurized fluid is connected to the first and second ports 24, 26, for example, via a pipe (not shown). The pressurized fluid is selectively supplied to either the first port 24 or the second port 26.

[0018] Furthermore, a cylinder bore (cylinder chamber) 28 is formed inside the cylinder tube 12, passing through it in the axial direction (the direction of arrows A and B). The cylinder bore 28 communicates with the first and second ports 24, 26 via connecting passages 30a, 30b.

[0019] The head cover 14 is manufactured by pressing a flat body made of a metallic material such as aluminum or the like, such that, when inserted into the cylinder bore 28, an outer edge portion is inclined radially outward at a predetermined angle relative to the axis of the cylinder bore 28, thereby biting into and being fixed to the inner peripheral surface of the cylinder bore 28. As a result, the head cover 14 is fixed near one end of the cylinder bore 28 in a state of blocking communication between the cylinder bore 28 and the outside.

[0020] The rod cover 16 is inserted into another end (in the direction of arrow B) of the cylinder bore 28 and is held inside the cylinder bore 28 by a lock ring 32 which is held in engagement with the inner peripheral surface of the cylinder bore 28.

[0021] A seal ring 34 is mounted in an annular groove on an outer peripheral surface of the rod cover 16. The seal ring 34 prevents the leakage of pressure fluid between the cylinder tube 12 and the rod cover 16. Furthermore, a rod hole 36 penetrates the rod cover 16 at its center, and the piston rod 20 is slidably inserted through the rod hole 36. A rod seal 38, mounted on an inner peripheral surface of the rod hole 36, is in sliding contact with the outer peripheral surface of the piston rod 20, thereby preventing the leakage of pressure fluid between the rod cover 16 and the piston rod 20.

[0022] As in the Fig. 1 to 3, the piston 18 has a cross-section corresponding to the cross-sectional shape of the cylinder bore 28. A piston bore 40 is formed at its center, into which an end portion of the piston rod 20 is inserted and secured by expanding (caulking). An installation groove 42, in which a piston seal 44 is mounted, is provided on the outer peripheral surface of the piston 18. The piston seal 44 is disposed near a substantially central position between one end surface and another end surface of the piston 18.

[0023] In addition, on the outer peripheral surface of the piston 18, a first step portion (first groove portion) 46, which is recessed by a predetermined depth from the outer peripheral surface, is formed on the side of an end surface (in the direction of arrow A) facing the head cover 14. A second step portion (second groove portion) 48, which is further recessed relative to the first step portion 46, is formed adjacent to the installation groove 42. Both the first and second step portions 46, 48 are annular, with the second step portion 48 communicating with the installation groove 42. In detail, as shown in Fig. 2, the outer diameter D1 of the piston 18 is the largest, the outer diameter D2 of the first step portion 46 is smaller than the outer diameter D1, and the outer diameter D3 of the second step portion 48 is smaller than the outer diameter D2 (D1 > D2 > D3).

[0024] The piston rod 20 consists of a shaft with a fixed length in the axial direction (the direction of arrows A and B), one end of which has a reduced diameter. The thinner one end is inserted through the piston bore 40 of the piston 18 and then deformed and expanded in diameter, thereby connecting one end to the piston bore 40. The other end of the piston rod 20 (in the direction of arrow B) is slidably held by being inserted through the rod hole 36 of the rod cover 16.

[0025] The piston cover 22 includes a disc-shaped main body portion (cushion portion) 50 made of, for example, an elastic material such as rubber or urethane, etc., a guide portion 52 formed at an outer edge portion of the main body portion 50 and bent at a right angle relative to the main body portion 50, and a hook portion 54 folded toward an inner peripheral side at the end of the guide portion 52. Specifically, the hook portion 54 is spaced a predetermined distance from the main body portion 50 in the thickness direction (the direction of arrows A and B) of the piston cover 22 and is formed substantially parallel to the main body portion 50. Furthermore, the main body portion 50, the guide portion 52, and the hook portion 54 on the piston cover 22 have a substantially constant thickness.

[0026] The base portion 50 is brought into abutment against one end surface of the piston 18. The guide portion 52 is installed to cover the outer peripheral side of the first step portion 46, and the hook portion 54 is mounted to cover the outer peripheral side of the second step portion 48, engaging with the second step portion 48, so that the piston cover 22 is integrally attached to the piston 18.

[0027] At this time, the outer peripheral surface of the guide portion 52 is shaped to protrude slightly from the outer peripheral surface of the piston 18, so that when the piston 18 and the piston cover 22 are inserted into the cylinder bore 28, the outer peripheral surface of the guide portion 52 is in sliding contact with the inner peripheral surface of the cylinder bore 28. Accordingly, the piston 18 is guided in the axial direction (the direction of arrows A and B), so that when the piston 18 is displaced toward the head cover 14 (in the direction of arrow A), the piston cover 22 abuts against the head cover 14 without the piston 18 directly contacting it.

[0028] The fluid pressure cylinder 10 according to the present invention is constructed substantially as described above. Next, the installation of the piston cover 22 on one end face of the piston 18 will be briefly explained.

[0029] First, as in Fig. 2, the piston cover 22 is disposed so as to oppose the one end face of the piston 18, and the hook portion 54 side (in the direction of arrow A) of the piston cover 22 is moved close to the piston 18. Next, the piston cover 22, in a deformed state in which the hook portion 54 is slightly pressed and expanded radially outward, is moved to the second step portion 48, stepping over the outer periphery of the first step portion 46. At the same time, the base body portion 50 is brought close to the piston 18 and brought into abutment against the one end face of the piston 18.

[0030] By releasing the deformation of the hook portion 54, the elasticity of the hook portion 54 engages the hook portion 54 with the second step portion 48. Accordingly, the main body portion 50 of the piston cover 22 abuts against one surface of the piston 18, the guide portion 52 is disposed on the outer peripheral side of the first step portion 46, and the hook portion 54 is engaged with the second step portion 58. Thus, the piston cover 22 is integrally secured to the piston 18.

[0031] Next, the operation and advantages of the fluid pressure cylinder 10 in which the above-mentioned piston cover 22 is attached to the piston 18 will be explained. As in Fig.1, a state in which the piston 18 is shifted to the side of the head cover 14 (in the direction of arrow A) and the main body portion 50 of the piston cover 22 abuts against the head cover 14 is referred to as an original position.

[0032] In the original position, by supplying a pressure fluid to the first port 24 by switching a switching device (not shown), the pressure fluid is supplied through the communication passage 30a between the head cover 14 and the piston 18, thereby pressing and displacing the piston 18 toward the rod cover 16 (in the direction of arrow B). In addition, the second port 26 is open to the atmosphere. At this time, by sliding contact of the guide portion 52, which is arranged on the outer peripheral side of the piston 18, with the inner wall surface of the cylinder bore 28, the piston 18 is guided with high precision in the axial direction (in the direction of arrow B). Then, the other end surface of the piston 18 is brought into abutment against the end surface of the rod cover 16, and the displacement end position is reached.

[0033] On the other hand, in the case where the piston 18 is displaced toward the head cover 14 (in the direction of arrow A) again by supplying pressure fluid to the second port 26 by switching a switching device (not shown), the pressure fluid is supplied through the communication passage 30b between the rod cover 16 and the piston 18, thereby pushing the piston 18 toward the head cover 14 (in the direction of arrow A). Accordingly, the piston 18 and the piston rod 20 are displaced together and integrally toward the head cover 14 (in the direction of arrow A), and the original position is restored upon abutment of the main body portion 50 of the piston cover 22 against the head cover 14.

[0034] In this case, one end surface of the piston 18 comes into contact with the head cover 14 via the base body section 50 of the piston cover 22, without the end surface of the piston 18 directly striking the head cover 14. Thus, the damping function buffers (absorbs) shocks that occur upon impact. Furthermore, the piston 18 is guided with high precision in the axial direction (in the direction of arrow A) by the guidance of the guide section 52.

[0035] In the manner described above, in the present embodiment, the piston cover 22 made of an elastic material is attached to the one end surface of the piston 18 facing the head cover 14 so that the base portion 50 is disposed on the one end surface, and the guide portion 52 provided on the outer edge of the base portion 50 is in sliding contact with the inner peripheral surface of the cylinder tube 12. Furthermore, the piston cover 22 has cushioning functions when the base portion 50 abuts the head cover 14, as well as a guiding function performed by the guide portion 52 during the displacement of the piston 18.

[0036] Compared with a conventional fluid pressure cylinder with a guide member (wear ring) provided on the outer peripheral surface of the piston 18, the provision of the piston cover 22, which has both a cushioning function and a guide function, allows the number of parts to be reduced. This reduces the number of assembly steps, thus simplifying the overall assembly.

[0037] Furthermore, since no separate guide element is required, it is not necessary to form an annular groove for installing such a guide element on the outer peripheral surface of the piston 18. This allows the piston 18 to be thinner in the axial direction. Combined with the thinner design of the piston 18, this also allows the longitudinal dimension of the fluid pressure cylinder 10 to be reduced.

[0038] In addition, since the piston cover 22 can be installed by engaging the first and second step portions 46, 48 formed on the outer peripheral surface of the piston 18, the production cost can be reduced, for example, compared with a case where a groove for installing a damper is formed in one end surface of the piston 18 by a cutting process (for example, face milling), because the first and second step portions 46, 48 can be formed with a lathe or the like from the outer peripheral surface side.

[0039] Furthermore, when the piston seal 44 is installed in the installation groove 42 from the one end surface side of the piston 18, the first and second step portions 46, 48 are provided with smaller diameters (D2, D3) that are recessed relative to the outer peripheral surface (outer diameter D1) of the one end surface side. Therefore, it is not necessary to expand the piston seal 44, and the piston seal 44 can be easily installed in the installation groove 42 located adjacent to the first and second step portions 46, 48 simply by slightly expanding it beyond the outer diameter D2 of the first step portion 46. Accordingly, the installation of the piston seal 44 to the piston 18 can be simplified. In this case, after the piston seal 44 is installed, when the piston cover 22 is installed, the piston seal 44 can be reliably prevented from falling off by the piston cover 22.

[0040] Furthermore, since the contact area (abutment surface) of the main body portion 50 of the piston cover 22 against the head cover 14 can be reliably increased compared to a conventional damper, the load per unit area can be reduced. In conjunction with this, the service life of the main body portion 50 can be improved because fatigue of the main body portion 50 can be avoided even in the case of a long service life. Furthermore, deviations in the holding position (and origin position) of the piston 18 in the axial direction, which are feared during such settling processes, can also be avoided.

[0041] Furthermore, there is no need to form a groove on one end surface of the piston 18 to facilitate the installation of the main body portion 50 of the piston cover 22. Since simple installation of the main body portion 50 is sufficient, the number of production steps and the production cost can be reduced, for example, compared to a conventional fluid pressure cylinder in which a groove for engagement and installation of the damper is machined by face milling.

[0042] Finally, since the base body portion 50 of the piston cover 22, which serves as a damping portion, is formed separately from the piston seal 44, the base body portion 50 and the piston seal 44 can be formed from different materials with different hardness properties according to the desired requirements. This allows them to be better adapted to the desired properties.

Claims

[1] Fluid pressure cylinder with: a cylinder base body (12) having a pair of ports (24, 26) for supplying and discharging a pressure fluid and a cylinder chamber (28) into which the pressure fluid is introduced from the ports (24, 26), a piston (18) to which a piston seal (44) is mounted in an installation groove (42) formed on an outer peripheral surface of the piston (18), wherein the piston (18) is displaceable in the axial direction inside the cylinder chamber (28), and a cover member (22) attached to one end side of the piston (18) and having a damping portion (50) that absorbs shocks caused when the piston (18) strikes the cylinder base body (12) at a displacement end position at which the piston (18) is displaced to one end of the cylinder base body (12), wherein a groove portion (46) to which the cover member (22) is attached is formed on the outer peripheral surface of the piston (18) and arranged adjacent to the installation groove (42), wherein an outer diameter of the groove portion (46) is smaller than an outer diameter of the piston (18), characterized by that the cover element (22) further comprises a hook portion (54) projecting toward an inner peripheral side of the piston (18), and that another groove portion (48) which is recessed radially inward relative to the groove portion (46) and to which the hook portion (54) is attached is provided on the outer peripheral surface of the piston (18) between the groove portion (46) and the installation groove (42). [2] Fluid pressure cylinder according to claim 1, characterized bythat the cover element (22) has a guide section (52) which guides the piston (18) in the axial direction of the cylinder base body (12), that the guide section (52) is provided on an outer edge section of the damping section (50) and is installed such that it covers a part of the outer peripheral surface of the piston (18), and that the damping section (50) abuts an end surface of the piston (18) which is oriented perpendicular to a displacement direction of the piston (18). [3] Fluid pressure cylinder according to claim 2, characterized by that the hook portion (54) is provided at one end of the guide portion (52) and is folded relative to the guide portion (52) to the inner peripheral side of the piston (18). [4] Fluid pressure cylinder according to claim 1, characterized by that the outer groove portion (48) has an outer diameter which is larger than that of the installation groove (42). [5] Fluid pressure cylinder according to one of the preceding claims, characterized by that the cover element (22) consists of an elastic material.

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